Centrifugal compressor construction



Sept. 20, 1949. I K. A. BROWNE 2,482,462

CENTRIFUGAL COMPRESSOR CONSTRUCTION Filed Nov. 9, 1946 ATTORNEY Patented Sept. '20, 1949 CENTRIFUGAL COMPRESSOR CONSTRUCTION Kenneth A. Browne, Lakewood, Ohio, assignor to Wright Aeronautical Corporation, a corporation of New York Application November 9, 1946, Serial No. 108,892

This invention relates to centrifugal compressors and is particularly directed to a centrifugal compressor in which the outer shroud or wall for the compressor impeller is formed integral with the impeller blades.

It is well known that centrifugal compressors, having an open-sided blade impeller surrounded by a stationary wall or shroud, are less eflicient than compressors of the type in which the walls, enclosing the impeller blades, all rotate with the impeller. However, if an impeller of this latter type is rotated at high speeds, the outer wall or shroud may be unable to withstand the centrifugal forces acting thereon. This is particularly true at the high rotative speeds at which aircraft engine superchargers operate.

An object of the invention is to provide a centrifugal impeller construction in which the outerenclosing wall rotates with the impeller and is adequately supported for high speed rotation. A further object of the invention comprises a novel impeller construction in which the outer enclosing wall of the impeller is formed integral with the impeller blades and the impeller hub.

Specifically, the invention comprises a centrifugal impeller having two parts suitably clamped together with the joint between the two parts disposed in a plane normal to the impeller axis such that each centrifugal impeller blade comprises two parts abutting along a radial line. One part of each impeller blade is formed integral with the forward wall of the impeller and a hub portion spaced radially inwardly from said Wall while the other part of each impeller blade is formed integral with the rear wall of the impeller and a second hub portion of-the impeller forms a continuation of said rear wall.

Other objects of the invention will become apparent upon reading the annexed detailed description in connection with the drawing in which:

Figure 1 is an axial sectional view through a centrifugal compressor having an impeller construction embodying the invention;

Figures 2 and 3 are views taken along lines 2-2 and 3- -3 respectively of Figure l; and

Figure 4 is a view schematically indicating the manner in which the impeller may be fabricated.

Referring to the drawing, a centrifugal compressor has an impeller made up of parts I0, I2 and I4 of which parts I and I2 are the main parts of the impeller. The impeller part III comprises a hub portion I6 having a substantially radially disposed annular wall I8 forming an integral continuation thereof. In addition, a plurality of cir- 6 Claims. (Cl. 230-134) cumferentially spaced vanes 20 are formed in- 2 tegral with the hub portion I6 and the annular wall I8. The impeller part I2 comprises a hub portion 22 and an annular wall 24 disposed radially outwardly from said hub portion 22 and having a radially extending portion axially spaced from the wall I8. A plurality of circumferentially spaced vanes 26 are formed integral with the wall 24 and the hub portion 22. Preferably, each of the vanes 20 and 26 is flat with its plane including the axis of the impeller. Also, each vane 20 abuts against a vane 26 and the junction line of each pair of vanes 20 and 26 is substantially radial, whereby each centrifugal impeller blade is a composite structure comprising a pair of vanes 2|! and 26.

With this two-part impeller construction, the annular wall or shroud 24 is connected to the hub 22 by the integrally formed vanes 26 thereby securing the wall 24 to the hub portion 22 against the centrifugal forces acting on the wall 24 during impeller rotation. Also, since the junction be.- tween the two impellerzparts I0 and I2 is normal to the impeller axis, the centrifugal forces acting on the impeller parts I0 and I2 during impeller rotation do not act to separate these parts except that these centrifugal forces tend to bend the radially outer portions of the vanes 20 and 26 and the walls I8 and 24 away from each other. However, the impeller parts I0- and I2 may be stressed when they are clamped together to resist this bending action of the centrifugal forces. To this end, the facing ends of the two impeller parts may be finished to a dished form-e. g., as illustrated in Figure 4. That-is, instead of the free ends-of the circumferentially spaced vanes 20 being finished to define a flat surface, their ends are finished to define a dished surface which is concave when viewed toward the wall I8. Similarly, the free ends of the vanes 26 are finished to definea dished surface which is concave when viewed toward the wall 24. With this construction, when the hub portions I6 and 20 of the parts I0 and I2 are tightly clamped together, these parts are stressed so as to resist bending of their radially outer portions away from each other.

The vanes 20 and 26 abut against each other whereby each impeller blade is a composite structure comprising a pair of vanes 20 and 26. Each pair of vanes 20 and 26 may be provided with a suitable junction to provide for their accurate alignment. Thus, as illustrated in'Figures 1 and 3, each pair of vanes 20 and 26 is provided with a lap joint indicated at 28 which may be welded, brazed or otherwise secured together.

The aforedescribed two-part centrifugal impeller construction permits relatively simple fab- 'necting impeller blades.

rication of an impeller in which the front and rear walls of the fluid flow path between the impeller blades both rotate with the impeller. As indicated in Figure 4, the impeller vanes of the part II can be formed from a solid piece by cutting radial grooves in the material at 30 thereby forming the vanes 20. Accordingly, the vanes 2| may be formedby a series of simple milling operations. The vanes of the part I! may also be formed by machining from solid material. Thus, the portion of the vanes 26, indicated at 32 in Figure 4, can be formed by a series of milling cuts similar to that forming the vanes 20. The remainder of the vanes 26 in the region 34 can be formed by a series of'milling operations with a relatively small cutter.

As illustrated in Figure 4, the facing ends 3| and 33 of the parts I! and I! are provided with the slight dished construction, previously described. With this dished construction, a butt joint preferably is substituted for the lap joint 28 illustrated in Figures 1 and 3.

. Withthe aforedescribed construction, the wall 24 providing the outer boundary of the fluid flowing through the impeller is integrally formed with the spaced impeller hub 22 by the intercon- This construction provides adequate support for the outer impeller wall even at the high rotative speeds at which air- \craft engine superchargers are operated. In addition, the construction of the present invention permits ready fabrication of the impeller.

As disclosed in applicant's prior U. S. Patent No. 2,398,203, it is desirable to provide a centrifugal compressor with an entrance vane section for graduallyimparting rotational velocity to the entering 'iiuid. Accordingly, a third impeller part l4 may also be provided. The impeller part comprises a hub portion 36 having vanes 38 extending therefrom. The entrance edges of the vanes 38 are curved in the direction of rotation of the impeller in order that the fluid enters the impeller substantially without impact with the impeller vanes. The downstream end of each curved entrance vane 38 terminates substantially tangent to the upstream end of one of the hat impeller blades 20, 26. As illustrated, the number of entrance vanes 38 is only equal to one half the number of impeller blades. For a more detailed'description of the desired curvature of the entrance vanes 38, attention is directed to applicant's aforementioned prior patent.

The entrance vane section [4 may be shrunk in place within a cylindrical extension 40 of the outer impeller wall 24. The outer edges of the entrance vanes 38 may have flanges 42 to insure better contact with the cylindrical wall 40. The three-part impeller is disposed within a conventional compressor housing shown in part at 44 and 46. Also, the three-part impeller is drivably splined to a shaft 48, the three parts Ill, and i4 being clamped by a nut 50 against a suitable shoulder 52 carried by the shaft 48.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my inventiomthat various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modification's.

I claim as my invention:

1. A centrifugal compressor rotor'comprising first and second partsarranged to be clamped together, said first part comprising a hub portion and an annular wall forming an integral continuation of said hub portion and extending radially outwardly therefrom, said second part comprising a hub portion and an annular wall spaced radially outwardly from said hub portion, said hub portions being arranged to be disposed co-axial and adjacent to each other with said second-mentioned wall axially spaced from and having at least a portion facing an outer portion of said first-mentioned wall, a set of circumferentially spaced vanes formed integral with the wall and hub portion of said first part, and a set of circumferentially spaced vanes formed integral with the wall and hub portion of said second part thereby joining said wall to said hub portion, the vanes of each set being arranged to extend from its wall into substantial abutting engagement with the vanes of the other set such that the vanes of one set form a smooth continuation of the vanes of the other set, the edges of the vanes of each set arranged to abut the facing edge of the vanes of the other set being fabricated so at to define a dished surface concave when viewed toward the wall integral therewith, whereby when said parts are clamped together said parts are stressed to urge their radially outer portions toward each other.

2. A centrifugal compressor rotor comprising first and second parts arranged to be clamped together, said first part comprising a hub portion and an annular wall forming an integral continuation of said hub portion and extending radially outwardly therefrom, said second part comprising a hub portion and an annular wall spaced radially outwardly from said hub portion, said hub portions being arranged to be disposed coaxial and adjacent to each other with said secend-mentioned wall axially spaced from and having at least a portion facing an outer portion of said first-mentioned wall, a set of circumferentially spaced vanes formed integral with the wall and hub portion of said first part, and a set of circumferentially spaced vanes formed integral with the wall and hub portion of said second part thereby joining said wall to said hub portion, the vanes of each set being arranged to extend from its wall into substantial abutting engagement with the vanes of the other set such that the vanes of one set form a smooth continuation of the vanes of the other set, the edges of the vanes of each set arranged to abut the facing edge of the vanes of the other set being fabricated so as to define a dished surface co-axial with the axis of said rotar and concave when viewed toward the wall integral therewith, whereby when said parts are clamped together said parts are stressed to urge their radially cuter portions toward each other.

3. A centrifugal compressor rotor comprising first and second co-axial parts arranged to be clamped together, said first part comprising a hub and an annular wall disposed about and spaced radially outwardly from its hub, said wall having an annular outwardly extending portion, said second part comprising a hub and an annular wall extending outwardly therefrom, said two hubs forming continuations of each other and the outer portion of said second mentioned annular wall facing and being axially spaced from said first mentioned outwardly extending wall portion, a set of circumferentially spaced vanes formed integral with the wall and'hub of said first part thereby joining said wall and hub, said vanes also extending axially from the annular outwardly extending wall portion of said first part toward said second part, and a set of circumferentially spaced vanes formed integral with the wall and hub of said second part and extending axially into abutting engagement with the first mentioned set of vanes, the junction of said two parts at their radially outer ends being between their outwardly extending annular wall portions and being formed at their abutting vanes.

4. A centrifugal compressor rotor comprising first and second co-axial parts arranged to be clamped-together, said first part comprising a hub and an annular wall disposed about and spaced radially outwardly from its hub,- said wall having an annular outwardly extending portion, said second part comprising a hub and an annular wall extending outwardly therefrom, said two hubs forming continuations of each other and the outer portion of said second mentioned annular wall facing and being axially spaced from said first mentioned outwardly extending wall portion, a set of circumferentially spaced vanes formed integral with the wall and hub of said first part thereby joining said wall and hub, said vanes also extending axially from the annular outwardly extending wall portion of said first part toward said second part, and aset of circumferentially spaced vanes formed integral with the wall and hub of said second part and extending axially into abutting engagement with the first mentioned set of vanes, the junction of the vanes of said two parts being disposed substantially in a plane transverse to the rotor axis and passing between the outwardly extending annular wall portions of said parts. l

5. A centrifugal compressor rotor comprising first and second co-axial parts arranged to be clamped together, said first part comprising a hub and an annular wall disposed about and spaced radially outwardly from its hub, said wall having an annular outwardly extending portion, said second part comprising a hub and an annular wall extending outwardly therefrom, said two hubs forming continuations of each other and the outer portion of said second mentioned annular wall being axially spaced from and having a shape similar .to said first mentioned outwardly extending wall portion, a set of circumferentially spaced vanes formed integral with the walland hub of said first part thereby joining said wall and hub, said vanes also extending axially from the annular outwardly extending wall portion of said first part toward said second part, and a set of circumferentially spaced vanes formed integral with the wall and hub of said second part and extending axially into abutting engagement with outwardly from its hub, said second part comprising a hub and an annular wall disposed about and spaced radially outwardly from its hub, the hub of said second part being upstream of and forming a continuation of the hub of said first part, and the wall of said second part having an annular outwardly extending portion axiall spaced from the outer portion of the annular wall of said first part such that said two walls and said two hubs form an annular open-ended space for the fluid to be compressed, the inlet end of said space extending primarily axially and the outlet end of said space extending primarily radially outwardly, a set of circumferentially spaced vanes formed integral with the wall and hub of said second part thereby joining said hub and wall, said vanes also extending axially from the annular outwardly extending wall portion of said second part, and a set of circumferentially spaced vanes formed integral with the wall and hub of said first part and extending axially therefrom into abutting engagement with the first mentioned set of vanes such that the one set of vanes forms a smooth continuation of the other set to partition said space into a plurality of passages extending between its inlet and outlet ends, the junction of said two parts at the radially outer end of said space being between their annular outwardly extending wall portions and being formed by their abutting vanes.

KENNETH A. BROWNE.

REFERENCES CITED The following references are of record in the file of this .patent:

UNITED STATES PATENTS Number Name Date 2,074,650 Holdaway Mar. 23, 1937 2,366,251 Fullemann Jan. 2, 1945 FOREIGN PATENTS Number Country 1 Date 462,853 Germany July 19, 1928 793,823 France Feb. 1, 1936 

